Primary Muscle Group: Core Muscles
Muscle groups worked in this exercise: Abdominus Rectus
Preparation: Lying on your back, bent your knees and place your feet on the floor. Hold the ball straight up above your chest. Bring both knees in toward your chest.
Execution: Now, extend your right leg, pull your belly button towards your spine, tighten and exhale. Inhale, bringing your right leg in to your chest and simultaneously extend your left leg. Make sure that your lower spine is always against the floor and that you keep the ball motionless as you move.
Comments: This takes real concentration, so tighten those abs and keep the ball stationary throughout!